Electric-arc-furnace electrode holder



Sept. 9, 1930.

ELECTRIC ARC FURNACE ELECTRODE HOLDER o. L. MILLS Original Filed March 5, 1929 1 ||r I 43 45 36 44 ,1a 4;-

l ig. E- 4 /r/ I I I N VEN TOR.

Oscarl.

A TTORNE Y.

Sept. 9, 1930.

0'. MILLS 7 1,775,437

ELECTRIC ARC FURNACE ELECTRODE HOLDER Original Filed March 5, 1929 2 Shoots-Shut 2 INVENTOR.

Oscar L. M245,

A TTORNEY.

Patented Sept. 9, 1930 UNITED STATES PATENT OFFICE OSCAR L. MILLS, OF LOS ANGELES, CALIFORNIA, ASSIGNOR TO MILLS ALLOYS 1170., OF LOS ANGELES, CALIFORNIA, A CORPORATION OF DELAWARE ELECTRIO-ARC-FURNACE ELECTRODE HOLDER Original application filed March 5, 1929, Serial No. 344,494. Divided and this application filed June 17, 1929,. Serial No. 371,540.

It is one of the objects of my invention to provide a furnace utilizing the electric are for melting substances, and especially to make it possible to secure a Working temperature neighboring 6000 F. Such a temperature is required for example, to melt tungsten, and to cause it to combine chemically with carbon to form the tungsten carbides. These materials are useful in connection with cutting or drilling tools (such as oil well drill bits) because of their extreme hardness.

I attain these high temperatures by a novel furnace structure that efiectively conserves the heat created by an electric are between electrodes, or between an electrode and the material being treated. I utilize not only the heat directly centered upon the material, but also reflected heat from the roof or ceiling of the furnace.

My invention possesses many other advantages, and has other objects which may be made more easily apparent from a consideration of one embodiment of my invention. For this purpose I have shown a form in the drawings accompanying and forming part of the present specification. I shall now proceed to describe this form in detail, which illustrates the general principles of my invention; but it is to be understood that this detailed description is not to be taken in a limitin sense, since the scope of my invention is est defined by the appended claims.

Referring to the drawings:

Figure 1 is a side elevation of a furnace embodying my invention;

Fig. 2 is a longitudinal section thereof;

Fig. 3 is a sectional view, taken along plane 3-3 of Fig. 1;

Fig. 4 is a sectional view, taken along plane 4-4 of Fig. 5, and

Fig. 5 is a rear view of a part of the furnace.

The furnace proper can include a lower base or container 11 of sheet metal, shown as in the form of a cup. The cover 12 is similar in form. There is a space between the opposed edges of the base or container 11 and the cover 12, although a number of straps 13 connect the two. Since the base and cover may be each connected to currentcarrying parts, there are insulating strips 14 between the straps and one of the elements 11, 12 so as to avoid short-circuiting between these parts.

The walls of the furnace are built in a multiple layer, as shown most clearly in Fig. 2. The outermost layer 15 can be made up of a layer of good heat insulation, not necessarily highly refractory; such as silocell bricks, which are made from diatomaceous earth. The second layer 16 can be built up from vitreous brick; and the innermost layer 17 should be made from highly refractory material, such as carbofrax brick. I have shown these layers 15, 16, 17 in a diagrammatic fashion; it is to be understood however that these layers are deposited brick by brick in container 11 and finally covered over by the cover 12.

These layers form a comparatively small furnace chamber 16 having an opening 19 whereby the operation can be viewed by an attendant. I prefer to utilize carbon electrodes between which an arc can form inside of the chamber 18. Thus there is a lower electrode 20 of carbon, projecting through an aperture in the bottom of base 11, and over it is disposed a thick layer or floor 21 of carbon dust or particles or both. Projecting through the top aperture 22 is an electrode structure 23. It is to be noted that this aperture 22 Widens at the bottom, so as to prevent any possibility of the electrode arcing to the inside edge of the aperture, and thereby short-circuit by way of the walls of the furnace.

The structure 23 includes a carbon core 24 that forms the electrode proper; it is rather tightly encompassed by an apertured bar 25, which is also preferably made from carbon. The core 24 projects slightly beyond the outer member 25, whereby an annular shoulder or surface 26 is formed, surroundin core 24 and spaced above its lower end. T e are is intended to be formed between the lower end of core 24 and material placed in contact with layer 21, and which is to be subjected to the heat of the are. This material 27 is in powdered or'granular form, as indi cated in my prior application, can be held in a carbon container 28. The circuit ,is completed between electrode 24 and electrode 20 through layer 21, container 28, material 27 and the arc itself.

I find that an arc voltage of between 30 and 40 volts is best; as it permits the surface 26 to be kept very close to the material 27, and thereby causes it efl'ectively to act as a heat reflecting surface. A further separation corresponding to larger arc voltages, would tend to reduce the effectiveness of this surface 26.'

The entire furnace can be supported on a framework 29. The upper electrode structure 23 is arranged to be axially movable so as to adjust the arc length. For this urpose, an electrode holder 30 is provided FFigs. 1, 2, and 3). It is formed as a split ring, with a tightening bolt 31 to clamp it tightly on rod 25. It can be water cooled, as by the provision of the water jacket 32, the inlet and outlets being generally indicated at 33 and 34. Bolt 31 also serves to connect a conductor 35 to the holder ring 30 so as to lead current to the structure 23.

The holder 30 is provided with spaced extensions 36, which have straps 37, 38 (Figs. 2 and 5) connecting them at the top and bottom surfaces. These extensions thus form a dgulde for a rack 39. A pinion 40 is supporte in the space between projections 36 and meshes with the rack 39. It is apparent that rotation of this pinion will cause the holder 30 tomove up and down, and consequently the electrode structure 23 is moved up and down.

Pinion 40 for this purpose is fast on a shaft 41, 'ournaled in pro ectlons 36. This shaft,

as s own most clearly in Figs. 3 and 5, has a pipe extension 42 to which a handle 43 can be fastened, for turning the pinion.

In order to make it possible to adjust the electrode structure laterally and to cause the arc to travel over the entire exposed surface of material 27, the rack 39 is movably mounted on to of the furnace cover 12. For this purpose it is rovided with a foot 44 through WllICll exten one or more guide pins or bolts 45. These bolts are fastened to the top of the furnace, and serve t(Tpermit a. slight freedom of motion to the structure 23. However, a sprmg 46 surrounds each bolt and exert-s a pressure to maintain the foot 44 pressed against the cover 12. Byappropriate manipu atlon of handle 43, the rack 39 can be tilted agamst the pressure of these springs, on any 0 the edges of foot 44, so as to adjust the position of the are on the material 27. In order to facilitate this adjustment, a counterweight 47 can be used on an arm 48.

When pinion 40 is rotated to adjust the position of electrode structure 23, this adjustment can be maintained as by the aid of a spring fin or 49 (Fig. 5) acting on a friction wheel 50 astened to shaft 41.

The lower electrode 20 is clamped into 8.

holder 51 that is entirely similar to the holder 30. This holder 51 can be fastened in any ap ropriate manner to the furnace structure. on tungsten carbide is to be made by the aid of this furnace, the mixture of metallic tungsten, tungsten oxide, and carbon is placed in a boat or container 28 and it is placed in the furnace. The operator then strikes the arc and through opening 19 observes its action on material 27. By experience he can manipulate handle 43 to keep the are moving over the surface of the material 27. As soon as the operator sees that the material becomes fluid, he pours it into a relatively cool mold. As the electrode surfaces on structure 23 wear or are disintegrated, the inner core or electrode proper 24 can be urged downwardly 'as b a mallet, so as to keep the vertical spacing 'etween its active end and the annulus 26 at the correct or best value. The entire assembly 23 of course can be lowered by pinion 40 as desired.

The surface 26 forms virtually the roof of the furnace. Since it is a carbon surface, it can withstand enormously high temperatures. The roof of the furnace is spaced close to the work, and acts to reflect the heat rays from the work without any consequent damaging deterioration of the electrode member 25.

In the present instance, the use of carbon for the electrode structures is needed for providing an atmosphere of carbon bearing gases in the furnace, whereby the formation of tungsten carbide is facilitated. However, the furnace as described can obviously be used for other processes where an extremely high temperature is required.

This application is a division of my appllication for electric arc furnace, Serial 0.

344,494, filed March 5, 1929, which is a con tinuation in part of my prior application, Serial No. 331,747, filed January 11, 1929 and entitled Process and apparatus for making tungsten alloys.

I claim:

1. In an arc furnace, a pair of electrode structures, and means for adjustably mounting one of said electrodes, including a mechanism for moving said electrode axially, and a foot member supporting said mechanism, and means providing a yielding force for holding the foot member in place, but permitting sal foot member to be tilted.

2. In an arc furnace, a pair of electrode structures, and means for adjustably mounting one of said electrodes, including a rack and a pinion, means for rotating the pinion,

a foot for the rack, and means providing a yielding force for holding the foot in place, but permitting said foot to be tilted.

3. In an electric furnace, a support, a stud extending upwardly from said support, electrode supporting means havin a base resting on said support, said base having an aperture larger than the stud through which the stud about the studs urging the base to rest flatly on the support but permitting it to be moved laterally or to be tilted thereon; and an electrode mounted upon said base.

OSCAR Lt. MILLS. 

